Electro-hydraulic steering systems are employed in work machines to provide smooth steering of the work machine under the control of an operator. In conventional work machines with electro-hydraulic steering, turning control is performed by an operator steering lever or other type of steering control mechanism. Even when under the control of the operator, however, the work machine can have instances where uncommanded steering or other motion can occur such that the wheels do not turn as commanded and the work machine does not follow the commanded path. For example, the work machine may move forward in a straight line when the operator tries to turn the machine. In other situations, the work machine may turn where no turn is commanded by the operator, or may turn in the opposite direction than that commanded by the operator. The latter turn anomalies may be particularly problematic due to the risks of hitting workers or structures near the work machine, or driving the work machine over surfaces or terrain that may cause instability of the machine, and may be symptomatic of failures in the steering control system of the work machine. Moreover, the uncommanded motion may be more problematic when the machine is operating at higher speeds where the operator has less time to react to and correct the uncommanded motion.
Control systems for hydrostatically driven and steered equipment are known in the art. For example, U.S. Pat. No. 8,818,632, issued on Aug. 26, 2015, to Dabbs et al., entitled “Detection of Uncommanded Motion of a Steering Motor,” teaches, in a machine having a differential steering control system, uncommanded motion may be determined by comparing an actual speed of a steering motor to a commanded turn direction signal from an operator. Where uncommanded motion is occurring, the steering motor speed and time-rate-of-change of the steering motor speed may be used to determine a weighted steering motor speed that is accumulated over a series of sample cycles and compared to an integration limit to determine whether the operator should be warned of the occurrence of uncommanded motion. The integration limit may be based on a factor indicative of the responsiveness of the machine, such as the oil temperature.
This system may detect uncommanded motion in a work machine having differential steering and warning the operator. However, uncommanded motion may occur in work machines having electro-hydraulic steering systems, and some types of uncommanded motion may be viewed as more problematic and may require a faster response from the work machine when the problematic situations occur.